instancy vs importunity

instancy and importunity both are nouns.

Word	Noun	Adjective	Verb	Adverb
instancy	Yes	No	No	No
importunity	Yes	No	No	No

As nouns, importunity is a hyponym of instancy; that is, importunity is a word with a more specific, narrower meaning than instancy:

instancy: the quality of being insistent
importunity: Quality of a person who is given to making importunate demands, being greedily or thoughtlessly demanding.

Other hyponyms of instancy include importunateness.

instancy (noun)	importunity (noun)
the quality of being insistent	Quality of a person who is given to making importunate demands, being greedily or thoughtlessly demanding.
the quickness of action or occurrence	insistent solicitation and entreaty